Radio azimuth indicator



Sept. 22, 1942.

w. P. LEAR 2,296,285

RADIO AZIMUTH INDICATOR Filed Dec. 28, 1939 2 Sheets-Sheet 1 INVENTOR. Mil/4M P Lil/f BY M ATTORNEY.

Sept. 22, 1942. w. P. LEAR RADIO AZIMUTH INDICATOR Filed Dec. 28. 1939 2 Sheets-Sheet 2 INVENTOR. W/LL MM R 464/? ATTORNEY.

Patented Sept. 22,1942

cr ate s cleans. This-intention relates lid-azimuthal indicators for radio.directionfindersandinere I II relates-to novel dual. indicators, combined with azimuthal compensators for y radio direction ers and airportloealizer systems. The dual azimuthal indicator of thepresent vention .is: particularly applicable. .for "use with radio lateral g idanceand; airport;-l.oca1i zer.. re. I ceiver systems; such.- as, disclosed in my co zaending;

applications Serial-Nos. 291 807 and-- 3Q,;i15, filed on August-'25,- 1939, and. spectively, and assignedto the; same. assignee I s this-case. r111: sucliisystems, two independently-r0 tatable. directionalantennae-rare nsed with indi l5 vidual 1 indicator needles arranged to give the latteralx guidance indications. ,In. accordance ;.with

the-'presentinvention, I provide-a, dual indicator having two .coaxial; pointers, each mechanically coupled to; a rotatable directional ant enna novel, rugged, foolproof azirnu to non-symmetrical nietal ic surrou di csafie the. directional antennape. A separate. quadrantal e na c a a y mo nted 1d eadacces bilim Other practical features are incorpora eii k he indicator arrangement of my, inyention. .Thea housing of the indicator is used as a: ionction box and controlhead-incorporating controlsnf or the radio guidance system. 2A. separate. adjustable scale; concentric withrthemainbearingscale, is

arranged in a'fioating'position in thecover of the: indicator to givereadings corrected ionmagnetim? deviations, as will be explained hereinafter: EThB combination indicator-control head-is; arranged 1* for horizontal or vertical mounting inthecockpit of the'aircraft'. '2 i? The foregoing and other -featurea-Fadvantages andbbjects of the -15resentf invention will be ap-'-' 1 parent in the following detailed description ofprferred embo'diin'enfthereof illifsti'ated"'in*fli drawings,-in'wl iiohi Fig. I isai'ront face v'i ew'of the Fig 2. is a' bottom View 'oi-"the th base removed. I' II I I 3.1 a i r edl ps F 9 al..Y W"" r h 1 .5 i l i flf' shower. 1 11. n ed. quadrantal 'en t'r, coirr'ec i mechanisms, taken: alohg tl e line'3 -3 of rig. 'i Fig.-, A. is n fcnlarze ro's'ssctionalf view rd h-th bearin adiu tor, f, he 'in'di a q g 4 h it Ratio n? In DI A b f illr anii-P." Liar, Dwain, Ohio, 'assiznor,'-by niesne s'ssi nmenimo Lear-Avie "corporation otalllinois: I I H I win ers. 1939,:Serialilf1o.311.331 1 I ciiilarly ff N ve e 7 ,39,

' flexible transmission shafts; an

1-20 v 53- Of O @1 1 291.807. Indicator needles 2!},

a. in error compensator ais -used for; each r otatab1..= .n-2

5 either dispensed with or 4 left 2| marked JQDM,

Fl. 25o--'11) chart for calibration.

indi tional;..antennae..

tions such system, forexamplaisjjthe basis 01 my. copending applications; Serial NOS .v 291,807 so tworotatableantenn'ae' is coupled to. a corre'-' sponding mechanical cable If and; H, ,in 'turn mechanically coupled to indicator"' r'ieedles 20. and Z I respectively of l the indie illustrated ,enibodimentfofthe' Mechanical cables .10; and

invention.

guidance indications. for, the

preach and landing maneuvers application. The angular positio 20; ll assume, are made to c angular positions of the 'as'so antennae atlany' 'given'instant; of the directional antennaein turn I I dependflupoh the'lateral position oi the aircraft I I statioi'is. indicator needle 20, marked In,

inner ground radio transmitter station} and invention applicable for terns in general. "Onlyga s such as needle 2 I couple o may be used for a singl I "antenna oi aregular radio'dire tern} The orientation of the antenna may controlled matlcally In this case, the second 'n'eedleillis ciated directional antenna. Needle extendedfasindicated in dotted lines at 2|, to I reciprocal hearings on the radio stations; Thelletters QDE" fers tosuch recipro responding marks, tionally be used.

cal bearing indications. Cor- Fig. '5 illustrates can t e" stated; with" a I catoroftl'ie present inventionjmay' be. usedwith a radio lateral guidance orrunway' lo-' I5 caliger-usystem employing two 'r'otat'able direc- ;Two indicator needles are o'perated by'the o a b e a tclilialto eflfectthej lateral guidance and localizing indica-j' s ns tut n th ll arelessentially d correspond to, "Fig.2, orjshafts ati on'; Serlal No. 2] give. thejla'teral' blin a o L ri set' iorthflin w hin ed esff orrespond to 'thej ciated directional T e fi i i ns I I I I with respect 3M th s ciated g ound'jtransmitter I I I ismechani-" cally'coupled to the'loop' antenna tuned to' the I idle. ouv needle, referring to directional bearings on radio stations -tuned-in on the'as'so- 2l m ay be marked on extension 2| re- The indicatorl amembly is housedin the" bok.

cture l5, enclosing quadrantal error compenular rotatable antenna, installation are deterrs individually coupled between indicator mined during the installation thereof on the iles 20, 2| and their respective loop shafts vehicle. A quadrantal error corrector is incorll. Indicator box I5 is used also as a juncporated between each of the rotatable loop anbox for carrying meters, control buttons 5 tennae and its associated indicator needle. The interconnections between cables from comcorrector mechanisms disclosed in the novel coent sections of the radio receiver apparatus. axial arrangement in a single control head are :trical plug l6 effects electrical connection individually useful- ,separately.,,.,,.s ;;,l ,,v separate veen external cable l1 and the instruments application thergio'r'ffis schemati any icated in .wiring of junction box l5, through receptor my copending application, Serial No. 286,733,

filed on July 27, 1939, assigned to the same ashe dual-needle indicator arrangement or my slgnee as this case, particularly in Figs. '1, 8 and sent invention is associated with other con- 9 thereof,

L components to form a control head for op- Fig. 2, a'bottom plan view of the indicatortion as a lateral guidance, runway localizer 01' control head ,withthe base removed, shows the acti n fi d ys The plu ality of concoaxially; arrangedquadrantal error compenls are asse b d to facilitate the p ration satorsior the loop antennae connected to flexe y a y p Master Switch 15 i5 ible cables 10 and (and indicator needles d to turn the sy 1" and and II." Fig. 3 is an enlarged cross-sectional ltIO]. the level or volume there f ough vari- 20 view through the indicator-control head. The .e resi ta e M mellnted in en quadrantal mechanism'coupled'to cable lfl essen- ,Josite corner of housing I5, is essentially a n e swmtn g 33 lin meter or m e e avp z the pilot rectly connected witficabl'e l-l'through remove ten he s p pe y tuned-in. as w as the able coupling unit-u: wot-mica: meshed with ative distance of the aircraft to the station. 5 worm 3g; and pivQtauy-nked corrwto-r a 35, :ter 26 corresponds to meter 0 of Fig. 9 of 31, 3|,- yieldably connecting'w'o'rm gear 35 a direction system disclosed in my application, with axial rod 401- End ll or arm-3c is rigidly.

r al N0- secured to worm gear 35'. Arm II is mechani- Io le swi 21 and 28 are located in cally engaged with ax'ial-rod" through the fric- 181 corner of indicator-junction box l5. When 30 ti nai arrangement" coinprlsing' thumb-screw 43 ggie switch 21 is moved to position Nav.," coroperating in the" slotted-end" o a 3g I pen ng o a a y the receiver System Cam follower It is" rotatably- -n' ounted on the operated as a normal radio direction indicator, g y- 'm iegu et e ar 31:: 3 ntrol ine he orientation of one of the direc Follower is ar'rangedftb ri'deagainst the cali- I )nal an en a the One coupled to flexible 35 brated inner edge oif hollowcam A tension raft H and indicator needle 2|. With this posispring "S m-arranged to rfi'ehhanffigllybias oppom of sw t L the dilleellienal receiver 5y5tem site arms and 3! together to pressfollower 4| placed in circuit connection to move needle mm mmm' g memi-w inner cam ll' to g ve directional bearing indicationssurface. indicator-needle ""is secured to the hile needle 20 rema ns stat one when 4 projecting'tip of axial-Tod- 40. Cam linis'calivltch 2 is mov d 0 Position marked brated forthequadrantal'error corrections to be irr sp n s t d e." the circuit conneeefie'cted on'indicato'rlfi with respectto the bear ons within junction box l5 are arranged to has g A a m- 'mg e t the -.1 invert the receiver into a radio lateral guidance responding ng 'r: positionsthe associated Istem, such as disclosed in my copendins ep 45 loop antenna connected -tofiexible shaft-L The ation, Serial No. 291,807. Both indicator needles b t p u e-emf: t cam 111 ii and 2| are thereupon operated, providing the scribed i qn'ne' flidn'witfi 155; iteral guidance and runway localizer indications R t tion or" tha l p" antenna. om-m tedv t pp h d anding maneuvers. Tog cable Ill in accordance wlththereceived' radio" witch 28 is the noise limiter switch which, when i nals, manually" or automatically; correspond a the Limiter" position, Cuts n the high ingly rotates worm gear 35,- Pivoted arms 38', 31,

requency components attendant with noisy sig- 33, 3g r d; und .withfigear 15 du t '1' lal reception. arm 35, rotating ln'dl'ca'tor' rod. 10. The angular In the fourth corner of the face of indicatordisplacement'of r d 4Q de e d up n th angular :ontrol head I5 is located manual Bearing 'position of'gear'fl and the'rel'ation between cam :ontrol 19 for adj the Position of annular 45' and its coacting. followers: The radial dis novable scale 30 of the indicator. The use of placement of follower H-dependsupon the shape :ontrol knob 29 will be explained hereinafter. f the engaging edge. of-cam1l5. The angular e a further control is provided through crank 3|. relation between rod 40 and gear 35 is varied by 1- Drank 3| is directly coupled to loop shaft II for th di displac ements quail-Ema) .ewox

manually changing the position of the associated t n, 1 either t clockwise grommet? L loop antenna, as will be described. The plurality clockwise direction; is between. the loop of controls and indications provided in the" comantenna, and its indicationnegdlejgpany bearing p gement are very useful for the busy position of the loop antenna, by gaglibrating the pilot. Most of the radio-navigation controls and radial contourof the cam-so that for each-angulndications are combined on a single head for lar position o{- ..th .,1 p antenna, 'or'iding lateral and directional guidance. correct reading by the indi'cato An important feature of my present invention tained on scaleshand resides in the novel mechanism efiecting A quadrant error om-reg azimuthal compensation for quadrantal errors between the secondloopan for the rotatable loop antennae. Quadrantal ible cable H and'its"associat e errors, as is known to those skilled in the art, 2|. The second corrector'f is'si result from the usual nonsymmetrical arrangejust described. and compri ment of nearby metallic objects about the anwith loop cable I] throug r V tennis. Quadrantal bearing errors for a partlc- 7 5 II; worm 52 on shaft";nieshedwith-w z g y 53 which is coaxial with rod 40 and located beneathrworm'z geanfl; and pivoted arms 54, 55, 56, 51-" coupled :between gear 53 and sleeve 58 rotatablyconcentric about rod 4.0. Sleeve 58 extends tbroughthe indicator to indicator needle 2l.- Arm- 54 is secured with gear 53 at connection 59.: 'Arm5'| is-frictionally engaged with tubularneedlei-sleeve 58 ,-through split friction coupling-66 controlled by thumb-screw 6|. Cam follower, 62 issrotatably mounted at the pivotal junctionof arms 55 and 56 to coact with the cammed edge of a cam 65. Tension spring 63, joined. between-arms 55 and 56 mechanically biases follower62 radially, against the edge of cam 65.

The two quadrantal error connectors are concentrically and compactly arranged within the unitary control head. The quadrantal error corrections afforded by each cam is effective for its particular loop antenna as installed, and for the frequency range of radio signals it is calibrated. The quadrantal error correctors herein disclosed are rugged, unaffected by vibrational stresses encountered in aircraft flight, and continuous in their quadrantal error compensations over the 360 degree scale. The concentric or coaxial arrangement of. the-correctors is effected through bell-shaped supporting member 10 having a plurality of successively wider stepped supports for earns 45 and 65, and spider 85. Member 10 may be continuous annularly, or in separate sections with leg portions for receiving the screw mountings for the units it supports. The weight of member In is reduced when thus made spoked or discontinuous.

The front face of the indicator control-head comprises three sets of concentric scales. Scale A is stationary, and inscribed on rectangular plate 15. It is graduated in 360 degrees. An adjustable scale B, also graduated in 360 degrees, is inscribed on-.annular ring 30, concentric with scale A, and floatingly supported in the front face. Scale C is stationary, with a zero index opposite the zero index of scale A, and arranged on fixed central disk 1|. Scale C is graduated to enable the pilot to quickly compensate azimuthal scale B for easterly or westerly magnetic variations and deviations. The indie cations by needles 20, 2| accordingly give correct azimuthal bearings on scale B. The bearings are corrected .for magnetic variations and devi ations for the vicinity where the readings are taken by theadjustment of scale B, and for quadrantal errors-in the radio frequency range used by the quadrantal error compensators.

Central disk .II is. secured to annular flange 68 extending inwardly from the corresponding end of stepped support 10. Bearing 12 in the centerof disk-"serves as one of the supports for the concentric needle shafts 40, 58. The opposite support for the needle shafts is bearing 83 mounted on=spid,er-85. Plate 60 is secured by screws H to theoutside of step 90 of member 10. Backplate 601s spacedly secured by screws 6| to frontiplate 15 with separating spacers 62. Outer face plate 15 is secured to box i5 by screws I4 attachedtofianges 13 on the plate; A back cover 861s secured to indicator box [5 by screws 61 through-flanges 66- on the cover. The spacers .82, provided between front plate 15 andback plate 80 afford a floating support for adiustableannular ring'carrying scale B. Scale B is thus controllably mounted between the opposed peripheral edges of disk H and plate 15, and between plates 15 and .60. Fig. 4 is an enlarged cross-sectional view through the scale B ring and its control means, taken along the line H of Fig. 2. Scale member 36 contains an annular projection 16 with gear teeth 1? edits inner peripheral edge for coaction with pinion 18 attached to shaft 19' of control knob 22:. The angular position of scale B with respect" to scale A is manually adjusted by Bearing? knob 29.- Scale C is used to assist'in the setting of scale B to correct for corresponding known magnetic variations and deviations for the vicinity.

The indicator arrangement of the invention is rendered compact by the-stepped supporting bell 10, which supports central circular disk ll on flange 68; plate on step earn 65, onthe next wider step 9!; cam '45, on the successively wider step 92; and finally spider'85, on the widest step 93. The stepped arrangement of the bellshaped member 10 presents a rigid integral me chanical structure for the indicator, permitting ready assembly of the components therein, and ready accessibility for servicing andmaintenance The mechanism is supported in oper-- thereof. able relationship independently of back cover 86.

A further important feature of the invention resides in theprovision of a direct manual control for a loop antenna mechanically connected to an indicator needle and a-qua-drantal error corrector mechanism. The preferred embodiment provides the manual angular control for the loop antenna connected to flexible cableil and the quadrantal error corrector including worm and worm gear- 52, 53.- Crank'handlelfl is an extended portion of rod 50"carrying worm 52. The pilot thus can directly adjust the angu lar position of the loop antenna independently:

of the automatic directional receiver, to manually obtain null bearings therewith, or adjust the loop for maximum signal reception to listen to radiosignals through, rain or static conditions; The indicated bearings of the loop antenna thus 'adjusted are corrected for magnetic and quadrantal errors.

The quadrantal error compensation effected by.

the disclosed corrector mechanisms is by a radialdisplacement of the cam followers to the degree determined by design of the coacting cam surface. Cam followers 44 and 62 are arranged to respectively operate against earns '45 .and 65-as shown in Figs. 2 and 3. An outward radial movement of the cam follower produces a correspond-- ing increased indication on the associated indicator needle. Thus, when cam follower moves outwardly radially, central rod 40 attached thereto is moved clockwise by a predetermined amount in correspondence withthe radial displacement of follower 4 4. Indicator needle 20 attached to rod 40 is thus advanced clockwise to give a positive quadrantal error correction, corresponding to the particular position of the loop antenna coupled to worm gear 35. A corresponding negative quadrantal error correction is effected by a decreased cam surface radius'with respect to the mean or 0 level of the cam.

A cam blank as supplied with the indicator prior to its quadrantal error calibration is illustrated at 95 in Fig. 5. Cam blank 95'contains three mounting holes 96for attachment in a predetermined position on the supporting bell l0. Cam blank 95 corresponds to the corrected earns 45 and 65, and are identified by differing outside diameters. The cam blank contains an inscribed annular calibration graph, etched'or otherwise imprinted thereon, as shown. The arcuate radial lines, spaced apart by 5 spacings from to 360, marks out the angular positions for the corrections. 0 is arranged to coincide with the azimuthal 0 of scale A.

The quadrantal error corrections to be imparted by the corrector mechanism are first determined in the usual manner by test measurements for the particular installation and frequency range of radio reception. The curve for correction is then readily plotted out on the graph of cam 95. The spaced concentric circles of the graph, marked 0, and 10, etc., re-

fer to the calibrations, in degrees, clockwise or counterclockwise for each angular position of the indicator and associated loop antenna. The arcuate disposition of the radial markings depends upon the'mechanical design and linkage of the corrector mechanism, taking'into account the law of-radial motion of the cam follower and the corresponding azimuthal compensations it imparts to the needle. After the calibration curve is plotted on the cam graph, the required cam shape is readily derived by cutting out the section of the cam between its peripheral edge 81 and the curve marked on the graph. An irregular calibrated cam surface results, corresponding to for example the irregular surface of cam 45 as shown in Fig. 2.

The indications on scale A give the true course or headings on the radio station, in degrees. In navigation it is preferable to refer the readings to the magnetic compass or directional gyroscope. The compass course heading in degrees,. is obtained directly from scale B. Scale B is adjusted by hearing control knob 29 until its index 0 is opposite the angular position on scale C corresponding to the correction for magnetic variation (for the geographic location in which the bearings are taken), as well as for magnetic deviation (for the particular magnetic compass 'installation) The setting shown in Fig, 1 is for a positive correction, corresponding to a combined westerly magnetic variation and magnetic deviation of 20, The pilot thus directly obtains the true azimuthal compass course on any angular reading on scale B, and may readily correlate this hearing with the magnetic compass true north heading for his navigating. The bearings by scale B are fully compensated for quadrantal errors due to the radio reception, for magnetic variations of the locality. and for magnetic deviations of the magnetic compass.

I am aware that the invention is amenable to structural changes and rearrangements, as well as for other specific applications falling within the broader spirit and scope thereof. Accordingly I do not intend to be limited except as set forth in the following claims.

I claim:

1. A composite indicating unit of the character described comprising: a first quadrantal error corrector, a rod coupled to said first corrector; a second quadrantal error corrector, a sleeve concentrically arranged about said rod and coupled to said second corrector; a frame rotatably supporting said sleeve and said rod with'corresponding ends thereof projecting through to the exterior of the unit; and first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit.

2. A composite indicating unit of the character described comprising: a first quadrantal error corrector, a rod coupled to said first corrector; a second quadrantal error corrector, a sleeve concentrically arranged about said rod and coupled to said second corrector; a frame rotatably supv f porting said sleeve and said rod with correspond- 1 ing ends thereof projecting through to the exterior of the unit; first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the I:

unit; first and second shafts rotatably mounted in said unit, elements fastened to said shafts and respectively coupled with said correctors, andter described comprising: a firstquadrantal'error corrector, a rod coupled to said first corrector; a second quadrantal error corrector, a sleeve concentrically arranged about said rodand coupled to said second corrector; a-frame rotatably sup-. l

porting said sleeve and said rod with corresponding ends thereof projecting through to the exterior of the unit; first and second indicator needles respectively attached to said correspond ing ends of said sleeve and rod externally of the unit; and an adjustable annular scale concen-.

trio with said needles for setting-up magnetic reading compenastions, whereby quadrantally and magnetically compensated azimuthal bearings are directly available on a common scale.

4. A composite indicating unit of the character described comprising: a first quadrantal error corrector embodying a first gear and asso.

ciated first mechanism, a rod coupled to said first mechanism, said gear being rotatably mounted about said rod; a second quadrantal error corrector embodying a second gear and associated second mechanism, a sleeve concentrically arranged about said rod and coupled to said second mechanism; said second gear being rotatably mounted about said sleeve, coaxially with and spaced from said first gear; a frame rotatably supporting said sleeve andsaid rod with corresponding ends thereof projecting through to the exterior of the unit; and first and second. indicators respectively attached to said corresponding ends of said sleeve and rod externally of the unit.

5. A composite indicating unit of the character described comprising: a first quadrantal error corrector, a rod coupled to said first corrector; a second quadrantal error corrector, a sleeve concentrically arranged about said rod and coupled to said second corrector; a frame rotatably supporting said sleeve and said rod with corresponding ends thereof projecting through to the exterior of the unit; first and second indi-' cator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit; first and second calibrated cams, a supporting bell mounted withinthe unit spacedly carrying said first and second cams in respective coaction with said first and second correctors to control therelative indications of said needles.

6. A composite indicating unit'of the character described comprising: a first quadrantal error corrector embodying a first gear and associated first linkage mechanism, a rod coupled to said first mechanism, said gear being rotatably mounted about said rod; a second quadrantal error corrector embodying a second gear and associated second linkage mechanism, a sleeve concentrically arranged about said rod and coupled to said second mechanism; said second gear being rotatably mounted about said sleeve; a frame rotatablysupporting said sleeve and said rod with corresponding ends thereoi projecting through to the exterior of the unit; first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit; first and second calibrated cams spacedly mounted within the unit in respective coaction with said first and second mechanisms to cont-rol the relative indications needles.

'7. A composite indicating unit of the character described comprising: a first'quadrantal error corrector embodying a first gear and associated first linkage mechanism, a rod coupled to said first mechanism, said gear being rotatably mounted about said rod; a second quadrantal error corrector embodying a second gear and associated second linkage mechanism, a sleeve concentrically arranged about said rod and cou pled to said second mechanism; said second gear being rotatably mounted about said sleeve, co axially with and spaced from said first gear; a frame rotatably supporting said sleeve and said rod with corresponding ends thereof projecting through to the exterior of the unit; first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit; first and second internal calibrated cam plates, a supporting bell mounted within the unit spacedly carrying said first and second plates in respective coaction with said first and second mechanisms to control the relative angulanindications of said needles with respect to the angular positions of the associated gears.

S. A composite indicating unit of the character described comprising: a first quadrantal error corrector embodying a first gear and associated linkage mechanism, a rod coupled to said mecnanism, said gear being rotatably d about said rod; a second quadrantal corrector embodying a second gear and ciated second linkage mechanism, a sleeve itali arranged about said rod and cousecond mechanism; said second sear being rotatably mounted about said sleeve; i'rarne rotatably supporting said sleeve and of said said rod with corresponding ends thereof projecting through to the exterior of the unit; first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit; first and second shafts rotatably mounted in said unit, gearing elements fastened on said she ts and respectively engaged with said gears, and means for removably coupling said shafts to remote individual rotatable directional antennae; and first and second calibrated cams spacedly mounted Within the unit in respective coaction with said f? and second mechanisms to control the relati angular indications of said needles with respect to the angular positions of the associated directional antennae.

9. A composite indicating unit of the character described comprising: a first quadrantal error corrector embodying a first gear and associated first linkage mechanism, a. rod coupled to said first mechanism, said gear being rotatably mounted about said rod; a second quadrantal error corrector embodying a second gear and associated second linkage mechanism, a sleeve concentrically arranged about said rod and coupled to said second mechanism; said second gear being rotatably mounted about said sleeve; a frame rotatably supporting said sleeve and said rod with corresponding ends thereof projecting through to the exterior of the unit; first and second indicator needles respectively attached to said corresponding ends of said sleeve and rod externally of the unit; first and second shafts rotatably mounted in said unit, gearing elements fastened on said shafts and respectively engaged with said gears, and means for coupling said shafts to remote individual rotatable directional antennae; and first and second calibrated cams spacedly mounted within the unit in respective coaction with said first and second mechanisms to control the relative angular indications of said needles with respect to the angular positions of the associated directional antenna; and a crank secured to one of said shafts and extend ing externally of the unit for manual rotation of the associated directional antenna.

WILIIANI 

